Almost all electronic devices use one or more voltage regulators to provide one or more specified DC voltages, for their intended operations, from a power source such as a battery. Among different types of voltage regulators, switching voltage regulators are particularly popular due to their higher efficiency. A switching voltage regulator may employ a switching element, such as a metal oxide semiconductor field-effect transistor (MOSFET) and an energy storage element including an inductor, a transformer or a capacitor between the source and the load. In a switching voltage regulator, the regulation may be performed by varying a duty cycle and/or a frequency of the switching element to control an output-to-input voltage ratio of the switching voltage regulator.
Switching voltage regulators can be constant frequency or non-constant frequency switching regulators. The non-constant switching regulators have faster transient response, compared to the constant frequency switching regulators, and can operate at a lower duty cycle. The non-constant switching regulators can achieve an approximately constant frequency operation through the use of a flexible one-shot timer (OST) that can control an ON-time of the switching element. The use of the OST enables operation at a rather low duty cycle that allows converting a high input voltage to a relatively low output voltage. The switching frequency, however, may still vary significantly due to second order effects in the switching regulator.
Many applications work with a number of parameters such as an input voltage (Vin), output voltage (Vout), switching frequency and the like, for which the OST has to be able to provide a wide range of pulse widths. For example, a buck regulator may need to support an ON-time within a range of about 25 ns to 2.5 μs. Supporting a broad range of pulse widths with a conventional voltage- or current-controlled OST may be challenging and may require a high OST gain. Providing a high OST gain may add jitter or may involve using a large low-pass filter, which increases cost. Therefore, it is desirable to cover a wide range of applications with a low phased locked loop (PLL) closed-loop gain.